“Remember the calamity of the great tsunamis. Do not build any homes below this point,” warns a stone tablet in the hamlet of Aneyoshi. As the Associated Press reports, many villagers heeded this advice. One man said his family moved their inn to higher ground a century ago — Aneyoshi was pummeled by a huge wave in 1896.

Some of the markers, like the one at Aneyoshi, were meant to function as yardsticks. Others simply memorialized past disasters and warned of the need to be vigilant.

Longtime coastal residents, as well as scholars who have studied the old tablets, note that the last serious tsunami to hit Japan was in 1960, and even that was relatively weak, generated by an earthquake off the coast of Chile. Those who experienced Japan’s most powerful tsunamis previous to this died years ago. And, as scholars have noted, in many places the old warning markers went unheeded.